Runningman
Member
Try some better ammo such as some sort of M193. The 55gr PMC Bronze I recently ran over my chronograph only clocked about 2817 FPS at 14 feet out of a 16" AR. Mighty pathetic 55 grain ammo if you ask me.
AR-15 Short stroking...? Whats going ON!?
- Thread starter MoDerN_WarRioR
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cottonmouth
Member
I had a 20 inch AR that was short stroking. I had an extra buffer spring that was a little shorter, by 2 or 3 coils. Put it in and she runs perfect now.
J.B.
J.B.
Omaha-BeenGlockin
Member
Easiest thing to try---use Breakfree liberally on the whole bolt/carrier assembly---run it wet and see what happens.
Be sure to work it into the extractor.
Be sure to work it into the extractor.
Last edited:
Bartholomew Roberts
Member
OK, you have made several contradictory statements. It is going to be difficult to tell you what is going on when you are telling us different stories about what is going on.
Assuming the second quote is the correct one, the first step is to confirm that it is short-stroking. You do this by loading a round in the chamber and an empty magazine. Check to see whether the bolt locks back after firing. If it does not, then combined with your earlier statements, this is probably short-stroking.
On a DPMS, the first place I would look is the gas key on the bolt carrier. DPMS does not stake this part and the gas key can come loose. Verify that the gas key and gas key screws are all tight. From here work your way along the flow of the gas looking for possible leaks in the system. (Check out the animated cutaway of an AR15 firing in the Rifle Forum Reading Library if you aren't sure about how the gas flows).
If the gas key is tight, then look for obstructions in the gas key or gas tube. I've seen popped primers get in there and jam things up good, and it can be tough to diagnose. Another common cause is people getting overzealous with cleaning and stuffing q-tips, etc. in the gas tube/gas key so that parts of them end up stuck in there.
Check the front sight block and the gas tube there to make sure there are no leaks.
If none of that pans out, pull the buffer spring and measure it. The acceptable range for a normal carbine buffer spring is 10 1/16 inches (25.56 cm) minimum to 11 1/4 inches (28.58 cm) maximum.
One other question: What type of magazines were you using and did the problem occur with a single magazine or more than one magazine?
If having the gas rings lined up causes a problem, then the rifle is marginal in some other area as well. A "healthy" AR will run reliably with a single gas ring. If staggering the gas rings on an AR "fixes" something then you can bet there is still another problem to be solved in the gas system.
Assuming the second quote is the correct one, the first step is to confirm that it is short-stroking. You do this by loading a round in the chamber and an empty magazine. Check to see whether the bolt locks back after firing. If it does not, then combined with your earlier statements, this is probably short-stroking.
On a DPMS, the first place I would look is the gas key on the bolt carrier. DPMS does not stake this part and the gas key can come loose. Verify that the gas key and gas key screws are all tight. From here work your way along the flow of the gas looking for possible leaks in the system. (Check out the animated cutaway of an AR15 firing in the Rifle Forum Reading Library if you aren't sure about how the gas flows).
If the gas key is tight, then look for obstructions in the gas key or gas tube. I've seen popped primers get in there and jam things up good, and it can be tough to diagnose. Another common cause is people getting overzealous with cleaning and stuffing q-tips, etc. in the gas tube/gas key so that parts of them end up stuck in there.
Check the front sight block and the gas tube there to make sure there are no leaks.
If none of that pans out, pull the buffer spring and measure it. The acceptable range for a normal carbine buffer spring is 10 1/16 inches (25.56 cm) minimum to 11 1/4 inches (28.58 cm) maximum.
One other question: What type of magazines were you using and did the problem occur with a single magazine or more than one magazine?
jdh said:
If having the gas rings lined up causes a problem, then the rifle is marginal in some other area as well. A "healthy" AR will run reliably with a single gas ring. If staggering the gas rings on an AR "fixes" something then you can bet there is still another problem to be solved in the gas system.
rcmodel
Member in memoriam
Myth.
You can aling the rings till heck freezes over and they will not be aligned after firing it a few times. They are constantly moving all the time and won't stay 120 degrees apart if you put them on that way.
And it doesn't matter anyway.
Like Avenger29 said, if everything else is right, it should still run, even with one ring missing and the two remaining ring gaps aligned.
rc
jdh
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So you guys must be much smarter than the guys who wrote the tech manual then.
The manual says to check for ring alignment and wear quarterly.
http://www.arjunkie.com/freepage/firearmdiagrams/M16 MAINTENANCE MANUAL.pdf
Section 2-7.
The manual says to check for ring alignment and wear quarterly.
http://www.arjunkie.com/freepage/firearmdiagrams/M16 MAINTENANCE MANUAL.pdf
Section 2-7.
They're still wrong. If I recall correctly, a military operator's manual that I have says to only lightly lubricate the rifle, which is incorrect.
Just because the .mil says to do it, doesn't make it right. They are very institutionalized and often reluctant to change procedures that ought to be changed.
The procedure for checking the gas rings is as follows, IIRC.
The gas rings are checked to make sure they are still there/in the right place and then the bolt is to be placed in the carrier and held with the bolt pointing straight down. If the bolt slides out, then it's time to replace the rings.
Just because the .mil says to do it, doesn't make it right. They are very institutionalized and often reluctant to change procedures that ought to be changed.
The procedure for checking the gas rings is as follows, IIRC.
The gas rings are checked to make sure they are still there/in the right place and then the bolt is to be placed in the carrier and held with the bolt pointing straight down. If the bolt slides out, then it's time to replace the rings.
cottonmouth
Member
I won't have to wory about the gas rings, I put one piece rings in both my AR's.
J.B.
J.B.
MoDerN_WarRioR
Member
Alright Guys. Alot going on in this thread. Alot of talk about the gas rings and the alignment and stuff... that's not really my issue on here. That is all not an issue with my problem. This is all very useful information but lets try to kinda get back on track just a little bit.
Ok, so... After inspection today i took everything all apart and inspected all the little pieces everyone suggested to check and all seems well.
- The bolt does not have a bunch of carbon build up around the pin hole
- The Gas block is very solid (no shifting) (also no i did not ever modify the block)
- I checked the key and nothing is loose or missing.
- The only concern for me is what is the best way to clean the inside of the gas tube out?
Barth, like i said in a previous post, that i didn't word my comment correctly so i know i had 2 conflicting statements. The second statement, the one that assumes short stroking is the correct statement. So when i get out to the range hopefully soon, i will try the one bullet in the magazine test to see if the bolt remains Aft or not.
Is there a way i can check manually if it is short stroking with out actually firing the weapon? i have snap caps so i don't have to use actual ammo. is there a way or no?
And also Canuck, why is it such a bad idea? I guess i was told incorrectly to lube up the buffer spring alot. I figured it will help ensure smooth flow of the buffer and prevent it from sticking (if thats the case.) AND i do live in Arizona so im not too worried with the temperatures dropping too low. LoL It was 73-74 degrees today in the mid December!!! CRAZY!
Thanks everyone for the answers! Lets keep the advise coming!
Im always down to try new options!
Ok, so... After inspection today i took everything all apart and inspected all the little pieces everyone suggested to check and all seems well.
- The bolt does not have a bunch of carbon build up around the pin hole
- The Gas block is very solid (no shifting) (also no i did not ever modify the block)
- I checked the key and nothing is loose or missing.
- The only concern for me is what is the best way to clean the inside of the gas tube out?
Barth, like i said in a previous post, that i didn't word my comment correctly so i know i had 2 conflicting statements. The second statement, the one that assumes short stroking is the correct statement. So when i get out to the range hopefully soon, i will try the one bullet in the magazine test to see if the bolt remains Aft or not.
Is there a way i can check manually if it is short stroking with out actually firing the weapon? i have snap caps so i don't have to use actual ammo. is there a way or no?
And also Canuck, why is it such a bad idea? I guess i was told incorrectly to lube up the buffer spring alot. I figured it will help ensure smooth flow of the buffer and prevent it from sticking (if thats the case.) AND i do live in Arizona so im not too worried with the temperatures dropping too low. LoL It was 73-74 degrees today in the mid December!!! CRAZY!
Thanks everyone for the answers! Lets keep the advise coming!
Im always down to try new options!Don't put anything in the gas tube other than something like Breakfree Powderblast/Gunscrubber/non-chlorinated brake cleaner. Do not stick any brushes, pipe cleaners, or the like down the gas tube.
And yet using the above chemicals in the gas tube is wasting them, for the gas tube will be blasted by the thousands of PSI of the gas coming back to work the action and it will be just as dirty as before. The gas tube is the part of the AR that is the only part of the AR that can be said to be "self cleaning" (you know, how the AR is mocked as).
The talk about the gas rings is because other posters (two) have given completely incorrect advice to do so.
Lubing up the buffer spring is a bad idea. The only thing it does is that it quiets down the "sprong", it does not do anything good for the rifle. It attracts dust and grime and that can cause issues, plus it can get on your clothes. You should not lube the spring/buffer beyond an extremely light amount for corrosion protection. I also suppose you could use a very light amount of dry film lubricant of some type for the same purpose. In short, treat the buffer springs like your mags- don't lube either.
Bartholomew Roberts
Member
There is no way. The whole point is that your gas system may not be receiving enough gas to cycle the action. There aren't too many ways of determining whether it is getting enough gas without giving it some gas to work with and that involves shooting.
How about the area where the gas tube goes into the front sight base? Is the roll pin securing the tube still present and does it look tight here? See a lot of carbon near that area (not like a little spot; but a fairly large smudge several times the size of the roll pin)?
Did you look inside the key for an obstruction? A popped primer will have a dull/shiny gray color and can be tough to spot in there.
I second everything Avenger29 said on this subject. If 15,000 psi of hot gas isn't going to clear it out of the way, I don't think you are going to have much luck poking at it with a q-tip.
By the way, what about the magazines? Did you use only a single magazine or several different magazines? What types of magazines did you use?
jdh said:
Well, I don't know who is smarter; but I do know which one of us is right on this particular point. A couple of things to realize jdh - first is that making changes to the manuals is a very involved process that doesn't happen instantly. Second, is that the manual you linked to is dated 1997 and we have had quite a few changes in the way we do M16/M4 maintenance since then. At the time that manual was written, things like the enhanced extractor spring for M4s didn't even exist.
jdh said:
Checking for wear is important. Ring alignment is meaningless. As others already pointed out, the rings rotate freely - so even if they were staggered when you put them in, what are the chances they will remain that way for the next three months? Likewise, if they did happen to align, chances are they would be unaligned by the time you got them out of the weapon. Totally nonsensical advice - and sadly not the only nonsensical advice the military puts out about M16s; but I don't want to derail the thread further by going into that subject.
Give a try yourself and see what you think.
Uncle Mike
Member
seriously guys....!!!
actually, worn rings result in symptoms quite similar to the one you described (the 2nd time)
i doubt that is your problem since it's a new gun, but you never know; the rings you have may not have been treated properly or something and may be prematurely worn.
the typical way people check is to take your BCG out of the gun, extend the bolt fully and stand it up on end (bolt down). if the friction of the rings is sufficient to hold the weight of the carrier up, then it's probably good. if the carrier slides down a bit, you need to put new rings in
cottonmouth
Member
I still say the buffer spring is too long or too strong, mine was a DPMS too. But it could be something else, I won't be mad if it is!
J.B.
J.B.
Check the buttstock screw hole is clear. If the compressed air can't be relieved, the rifle shortstrokes. Adding lots of oil to the buffer tube will obstruct it and seal things even more.
Use enough lube on the BCG from round one to make it wet. After 100 rounds, a dry bolt will collect enough carbon to start sticking. Don't run the gun dry.
The gas ring issue is overblown. I get the same complaints from customers who thought their tire stems should always point the same direction on every wheel. They had no clue about differing turning circles or the necessary action of a differential. Same thing here. The .mil manual says check them quarterly - not after every round shot. They move around and when compressed in the bolt carrier, seal well enough.
No, I don't know who started the crap about getting them separated, but then again, we had to scrape carbon off the bolt tail, too. It doesn't do anything. Most of what I was taught about cleaning the M16 ranks right along with using a drill driver and inserting the bore brush through the muzzle.
Clear the buffer tube hole in the stock screw, let it breath. Lube the bolt carrier and use it wet. Shoot it. It should work fine.
Use enough lube on the BCG from round one to make it wet. After 100 rounds, a dry bolt will collect enough carbon to start sticking. Don't run the gun dry.
The gas ring issue is overblown. I get the same complaints from customers who thought their tire stems should always point the same direction on every wheel. They had no clue about differing turning circles or the necessary action of a differential. Same thing here. The .mil manual says check them quarterly - not after every round shot. They move around and when compressed in the bolt carrier, seal well enough.
No, I don't know who started the crap about getting them separated, but then again, we had to scrape carbon off the bolt tail, too. It doesn't do anything. Most of what I was taught about cleaning the M16 ranks right along with using a drill driver and inserting the bore brush through the muzzle.
Clear the buffer tube hole in the stock screw, let it breath. Lube the bolt carrier and use it wet. Shoot it. It should work fine.
jdh
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Ok, a well maintained functional AR with no issues MAY run on one gas ring or with the rings aligned. One ring is going to flop aroung in the cut and tilt causing wear that is not normal. It is your gun if you want to run it way more power to you.
Worn rings can allow gas to leak through. The rings aligned will allow gas to escape. In an AR with a clean gas system this may not lower the pressure enough to cause functional issues.
A gas leak from an improperly fitted front gas block, worn, loose, obstructed key, or a gas tube blockage from build up or a kink, or any other number of things can cause low gas pressure in the BCG. The leakage around the rings added to the already low gas pressure can contribute to functionality issues.
All it takes is a few additional seconds during the re-assembly process to check an correct one of the potential problems. One that you do have control over.
I never said it would absolutley cause the problem. It is a potential contributing factor. But what do I know? I only have to keep the 12 worn out, dirty, abused range guns running, three days a week for 6 weeks out of the year, long enough for the 260 or so users to shoot their qual course.
Worn rings can allow gas to leak through. The rings aligned will allow gas to escape. In an AR with a clean gas system this may not lower the pressure enough to cause functional issues.
A gas leak from an improperly fitted front gas block, worn, loose, obstructed key, or a gas tube blockage from build up or a kink, or any other number of things can cause low gas pressure in the BCG. The leakage around the rings added to the already low gas pressure can contribute to functionality issues.
All it takes is a few additional seconds during the re-assembly process to check an correct one of the potential problems. One that you do have control over.
I never said it would absolutley cause the problem. It is a potential contributing factor. But what do I know? I only have to keep the 12 worn out, dirty, abused range guns running, three days a week for 6 weeks out of the year, long enough for the 260 or so users to shoot their qual course.
MoDerN_WarRioR
Member
Alright so after reading ALL the posts, there are a few easy things im going to try before heading to the range again.
1.) Im going to check the overall buffer spring length to make sure it has enough room to go fully back.
2.) Im going to mop up the oil out of the buffer tube to prevent it from gumming it up.
3.) I AM NOT going to que-tip or pipe clean the gas tube because those points about the HOT 15000psi gas pushing through is well enough advice to ensure me there probably isnt anything clogged in that tube.
4.) im going to run that thing wet! and as well im going to try my hardest to reduce any friction on any moving part with oil and or cleaning it even more than i do already.
OK so if i do find out my buffer spring is too long, how can i go about shortening it? maybe cutting of 2-3 coils of metal? But i dont want any burrs to add friction.
Also, i will take a look at my rings and ensure at that moment they are separated. but i do believe like many people have mentioned that they bounce around and shift and change direction from the shock of the gun, but worth checking. They could be worn as well like TALIV mentioned but, that i will deal with later if this stuff doesnt work.
ALSO: people have been asking which magazines i have been using and i got 2 PMAG 30 round mags that have been amazing. they seat nicely but do kind of rock somewhat... could this maybe be introducing a new cause to the problem??
Thanks guys!!
-Chris
1.) Im going to check the overall buffer spring length to make sure it has enough room to go fully back.
2.) Im going to mop up the oil out of the buffer tube to prevent it from gumming it up.
3.) I AM NOT going to que-tip or pipe clean the gas tube because those points about the HOT 15000psi gas pushing through is well enough advice to ensure me there probably isnt anything clogged in that tube.
4.) im going to run that thing wet! and as well im going to try my hardest to reduce any friction on any moving part with oil and or cleaning it even more than i do already.
OK so if i do find out my buffer spring is too long, how can i go about shortening it? maybe cutting of 2-3 coils of metal? But i dont want any burrs to add friction.
Also, i will take a look at my rings and ensure at that moment they are separated. but i do believe like many people have mentioned that they bounce around and shift and change direction from the shock of the gun, but worth checking. They could be worn as well like TALIV mentioned but, that i will deal with later if this stuff doesnt work.
ALSO: people have been asking which magazines i have been using and i got 2 PMAG 30 round mags that have been amazing. they seat nicely but do kind of rock somewhat... could this maybe be introducing a new cause to the problem??
Thanks guys!!
-Chris
feedthehogs
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Just for S&G's, I would try another brand of ammo.
I teach CCW classes and the ranges I've been going to all have been selling PMC bronze ammo.
In various calibers and .223 I've had consistant ammo failures with this brand(low charge in semi auto and hard primers in semi and revolver). Switch to another brand and the failures go away with the students.
A poorly seated or rocking magazine can lead to FTF's. I would also caution you about wetting down the AR too much. A little oil goes a long way.
I teach CCW classes and the ranges I've been going to all have been selling PMC bronze ammo.
In various calibers and .223 I've had consistant ammo failures with this brand(low charge in semi auto and hard primers in semi and revolver). Switch to another brand and the failures go away with the students.
A poorly seated or rocking magazine can lead to FTF's. I would also caution you about wetting down the AR too much. A little oil goes a long way.
The AR runs extremely well wet, especially once it gets filthy. That's wet on/around the BCG, not elsewhere, though. Lube in buffer tube or magazines? Not good. Lube in chamber/barrel, especially enough to cause an overpressure situation? Very, very bad!
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